Comprehensive analysis of MYOC gene in primary open-angle glaucoma

Abstract

Glaucoma is an optic neuropathy characterized by irreversible optic nerve degeneration, progressive visual field defects, and cupping of glaucomatous optic disc. This condition is a leading cause of blindness worldwide affecting ~67 million people with 6.8 million bilaterally blind. Primary Open-Angle Glaucoma (POAG) is the most common form of Glaucoma accounting for 70% of all cases in Caucasians. This type of Glaucoma comprises three subtypes: POAG with adult age of onset, Juvenile Open-Angle Glaucoma (JOAG; onset <35 years old) and Normal Tension Glaucoma (NTG; normal intraocular pressure). MYOC gene was the first gene identified as POAG causative and ever since approximately 99 sequence variations were considered Glaucoma causing disease mutations. The purpose of this study was to identify sequence variations in MYOC gene that may be responsible for the phenotype in a group of Portuguese POAG patients. In order to fulfil the objective of this work, 104 POAG patients were analyzed by a PCR-sequencing method. Additionally, 54 controls subjects were studied by a SNaPshot approach, followed by statistical analysis with GraphPad Prism v.6. Statistically significant differences were assumed when p < 0.05. Finally, in silico analyses were performed to investigate the evolutionary conservation, functional effects and transcription factor search in the most relevant variants identified. The sequencing results of the 3 coding exons and proximal splicing junctions of MYOC gene in 104 POAG patients allowed identifying 27 variants. From these, two variants are likely Glaucoma causing disease mutations and were identified in two NTG patients. A statistically significant association was found among females suggesting a possible protective effect (OR=3.29). Further studies are required to clarify the possible involvement of the identified variants in POAG etiology